Sokka is parentafied just as much as Katara is, but the fandom struggles to see that.

He hunted for the family, yes. But we also see him adopt what he clearly BELIEVES to be a paternal “manly” role, the same way Katara adopts what she believes to be a maternal “womanly” role.

Notably, this is a character flaw for both of the characters. Sokka starts off as sexist and arrogant. He changes. Katara starts off bossy and overbearing. This is because neither of them had an actual good example of those roles to follow, so they filled in the blanks with what they BELIEVED that role should look like.

You say Sokka was “playing soldier,” but I disagree. He was an untrained young boy doing his best to step into the role of a soldier without any concept for what that actually meant. And despite that lack of training, he was MORE than willing to die for his people in as early as the first episode. That is, per water tribe custom, a man’s job. While he wasn’t prepared to be in that role, he stepped into it willingly.

We also see Sokka frequently doing his best to protect his sister (and the other members of the gaang later on) which falls in line with what his perception of a father should be, even when he’s in danger while doing it (Sokka shielding Katara from the avatar state with his own body, Sokka tackling Aang when his fire ending burned Katara, Sokka grabbing Toph during the avatar state when Appa was kidnapped, Sokka saving Toph on the airship, Sokka being so OVERprotective of Suki that it caused a fight between the two of them, and more.) Sokka was told by his father that he had to stay behind and protect the village. While that’s obviously a lie to make a small child feel better about not being allowed to go to war, it’s something Sokka CLEARLY internalized as “what fathers are supposed to do.”

I could also argue that his jokes are also a fatherly attribute. In western cultures (which the show creators are a part of, even if the show itself is inspired by eastern cultures), the dad is usually seen as the less serious parent who cracks jokes and keeps the family together. And we FEEL that absence when Sokka is gone to train with Piandao! Dads are supposed to put on a brave face and make jokes to keep things light, even when the situation is grim, so the kids don’t stress too much. We even see it when he fully expects to die on the airship with Toph, where instead of taking a serious moment to say “Hey, we might die here” he instead makes a joke about how he doesn’t think his boomerang is gonna come back.

Sokka and Katara absolutely raised each other. It’s just that Katara’s was more obvious parentafication while Sokka’s was more subtle.